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12th September 2012 @ 02:06
The aim over the next few reactions is to compare reaction rate, conversion and yield varying reaction temperature and Yb loading MNR46-8, 10 mol% Yb at room temperature MNR46-9, flasks were mixed up therefore ended up being a duplicate of MNR46-10, stoichiometric Yb at reflux [b]Hazard Assessment[/b] [data]4992[/data] [b]Procedure[/b] To a solution of KAB22-1 (1eq) in HPLC grade acetonitrile (0.03 M) under argon at 0 °C , was added was added acetyl chloride (1.8 eqs), lutidine (1.4 eqs) and Yb(OTf)3 (01-1 eqs). The reaction was then stirred at room temperature or at reflux and aliquots taken at noted time intervals for LC analysis. Sample were taken up to 5 hours then the reaction were left overnight. Only MNR46-8 showed significant signs of product. Surprisingly, MNR46-10 showed signs of the product degrading over time (assuming the last data point is an outlier) MNR46-8 was worked up after 48 hours. The mixture was washed saturated sodium bicarbonate solution (10 mL) and the aqueous layer was extracted with ethyl acetate (3 × 15 mL). The organic fractions were combined, dried over MgSO4, filtered and concentrated under reduced pressure to yield a yellow oil, 0.329 g. TLC in 50% EtOAC/Hex. Spot left to right, lutidine, KAB22-1, co-spot, worked up MNR46-8, co-spot, product (MNR46-4). Two spots were seen in the SM spot, this can be put down to some hydrolysis in the TLC spotter sample as it was a few weeks old. TLC also show complete consumption of SM to two new spots, them being desired product and hydrolysis products. [data]5105[/data] Column in 40% EtOAc/Hexane Frac 1-7 - mainly CHO, not as much amine, volatile?? 0.049 g [data]5097[/data][data]5093[/data] Frac 9-18 - product with unknown peak at 2.25. Product appears to come up as two conformers in a ration of 2:1. This is clearer in the 13C. 0.080 g, 0.27 mmol, 34 % [data]5099[/data] [data]5101[/data][data]5095[/data] [b]Conclusion[/b] At 10 mol% the reaction IS catalytic, at room temperature the reaction takes about 2 days to go to completion. The reaction using 1 eq of catalyst appears to have a negative effect of the progress of the reaction or it degrades the product. This needs looked into further. ----------------------------- MNR46-9 quenched and worked up as normal but then volume reduced and washed with 10% citric acid. [data]5119[/data] one wash appeared to get rid of most of the lutidine, crude mass 0.190 g running the crude down a column yielded product but upon standing the product hydrolysed back to aldehyde and amine. Yields and masses not calculated. [data]5183[/data] see [blog]6671[/blog] for a fuller account and explanation.
Attached Files
mnr46-8 table.PNG